Cellular communication systems often require that base transceiver station (BTS) radio frequency (RF) signals be time aligned with each other. The timing alignment requirement may further require an accuracy of alignment on the order of a few microseconds to a recognized timing reference. For example, timing misalignment may result in signals associated with multiple mobile stations interfering with each other or may make it difficult for a mobile station to combine signals received from multiple base transceiver stations (BTSs). Cellular communication systems also may require that the RF signals be aligned to absolute time.
One known way of meeting these timing alignment requirements is through utilization of a timing synchronization reference signal that is broadcast system-wide, that is, a Global Navigation Satellite System (GNSS) signal such as a Global Positioning Satellite (GPS) signal, a Global Navigation Satellite System (GLONASS) signal, or a Galileo system signal. Typically, such signals are broadcast by a satellite system to the BTSs and require use of a timing synchronization antenna and receiver, such as a GPS, GLONASS, or Galileo system receiver, separate from a BTS's RF antenna and circuitry in order to receive the signal. The timing synchronization receiver is co-located with the BTS's synchronization circuitry in the BTS's digital subsystem, separate and apart from the BTS's radio, or RF, subsystem, so as to minimize error in the transfer of the timing reference signal from the special receiver to the synchronization circuitry. The digital subsystem is typically located inside a building where it is convenient for access, maintenance and connection to the digital sub-system interfaces. However, the timing synchronization antenna needs to be located outdoors with line-of-sight access to the satellite system in order to receive the satellite signal. A favorable location for the timing synchronization antenna usually is proximate to the radio subsystem, which may be anywhere from one meter to 20 kilometers, or more, distant from the digital subsystem, Traditionally, the cable connecting the digital sub-system to the timing synchronization antenna is a dedicated cable, and depending on the installation details, this cable can be a lengthy and expensive cable to install and maintain.
Therefore, there is a need for a simpler, less expensive method and apparatus for performing time synchronization that takes advantage of the potentially spatially diverse components of the wireless communication system to yield a lower cost timing synchronization solution.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required.
Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.